1. Field of Invention:
This invention relates to a relatively low cost container for dispensing a working fluid under pressure and a method for dispensing working fluid under pressure.
2. Prior Art:
Applicant's earlier pending application Ser. No. 709,093 discloses a fabric that can be used to cool areas of the body. The system injects into the fabric a liquid that boils at a relatively low temperature. Body heat causes the liquid to change phase (boil), which cools the skin. This same method is the basis of some of applicant's other patent applications and in his earlier U.S. Pat. Nos. 3,479,838 (1969) and 4,569,355 (1986).
In applicant's patents and pending application Ser. No. 673,509, the low temperature boiling has as its primary function to cool a small disk, which is placed against the skin. By cooling the small area of the skin and allowing blood flow to warm the skin after the device stops cooling the skin, one can measure peripheral blood flow. As a blood flow monitor, portability is usually not a major concern. Portability is more important for the more general cooling fabric if one does not want to be tied to relatively heavy, complex tanks.
Applicant's earlier application Ser. No. 673,509 discloses a vessel that holds two liquids, a refrigerant and a pressurizing fluid. A movable piston divides the two fluids. The pressurizing fluid has a vapor pressure higher than the pressure of the refrigerant so that the pressurizing fluid, which is part liquid and mostly gas, urges the piston against the refrigerant. As the refrigerant volume decreases, a portion of the pressurizing fluid changes phase from a liquid to a gas to replace the volume of the refrigerant dispensed. This replacement maintains a constant pressure, which is the vapor pressure of the pressurizing fluid when the refrigerant is dispensed. The pressure from the pressurizing fluid exerts force on the piston to maintain the refrigerant above its vapor pressure so that it remains in the liquid phase in the volume allocated to its storage. As the previous applications indicate, it is important to maintain the refrigerant in its liquid state so that it can only boil when it is injected into the cooling fabric or heat exchange disk. Therefore, it retains its value as a coolant in the liquid state until it reaches the precise location where cooling is desired. The increased pressure also allows the refrigerant to be transported from its storage tank for use at high pressures. Because the refrigerant is at higher than its normal vapor pressure, it can flow faster than lower pressure fluids would flow in a tube of a given cross-section. Also, liquid volume controls are more precise than gas controls. It is important to inject a controlled amount of refrigerant to regulate the rate of cooling.